EDEN PRAIRIE, Minn. -- Chris Cook is healthy this time, and the Minnesota Vikings' second-year cornerback seems to have his confidence back, too.

He's certainly not holding back on his expectations for how good he, Antoine Winfield and Cedric Griffin can be together in the Vikings' nickel defense this season.

"I talk with Antoine about that all the time," Cook said on Wednesday. "I was like, 'Man, we can go out and be the best three in the league if we all do what we know we can do.'"

It won't take long to find out if Cook is right.

Sunday's opener at San Diego will pit the Vikings' remodeled secondary against Pro Bowl quarterback Philip Rivers and a Chargers offense that finished last season first in the NFL in total offense and second in passing.

They boast a legitimate No. 1 receiving threat (Vincent Jackson), veteran secondary options (Malcom Floyd and Patrick Crayton) and a game-changing tight end (Antonio Gates), allowing them to spread the field and stretch zone coverage.

"They are a challenge for any defense, let alone when you're coming off of a situation we're coming off of from a health standpoint," coach Leslie Frazier said. "Terrific receivers. Terrific quarterback. Number one offense in the league a year ago. So, it'll be a challenge for us. We'll find out where we are in a hurry."

Health was a constant problem for the Vikings' cornerbacks last season.

Cook had two surgeries to repair meniscus tears. Griffin returned from one knee reconstruction only to blow out the other. Winfield stayed on the field but often worked the slot while the likes of Asher Allen, Frank Walker and Lito Sheppard played on the perimeter.

But the one full game the top three cornerbacks did play together, in a win over Detroit on Sept. 26, was pivotal in Frazier's mind when it came to trying to improve the secondary from within.

"It changes so many things from a defensive standpoint," Frazier said. "Our league has really evolved into a pass-first league in so many cities and so many teams. So, you better have some guys on the outside that can stand up. If you don't, no matter how good you are up front, it's just a matter of time before you're going to get exposed.

"Those three guys have the ability to be what we're looking for. They showed it when they were on the field."

Griffin held up OK in limited preseason reps, but Frazier acknowledged coaches are "anxious" to see how he performs in a full game. Cook gave up a touchdown in the exhibition opener and missed the finale with a hamstring tweak that apparently is a nonissue.

"A lot of the big receivers in the league, they like to throw jump balls to them and just put the ball up in the air for them whether they're covered or not," Cook said. "I'm looking forward to that happening a lot this year. I can't wait for this game on Sunday so we go out here and beat these guys and I can go out and show what I have."

The Vikings also will have a new starting safety, Jamarca Sanford, on Sunday in place of released veteran Madieu Williams. He figures to have his own challenges over the top, with Rivers sure to test Griffin and Cook on the perimeter.

"They're real explosive," Winfield said. "I want to say all their receivers are 6-4 or better, they have a really good quarterback, a really good tight end. It's going to be a challenge for us, but I'm sure we'll be up to it."